Variable inductance



1954 L. G. KETCHAM 2,666,187

VARIABLE INDUCTANCE Filed June 28, 1949 INVENTOR. LY MAN G. KETCHAM.

BY 1W4 away AA A TTORNEYSJ Patented Jan. 12, 1954 VARIABLE INDUCTANCE Lyman G. Ketcham,- Summit, N. J., assignor to 1 Automatic Manufacturing Corporation, Newark, N. J., a corporation of New Jersey Application June 28, 1949, Serial No. 101,713

11 Claims. (01. 336-136) The present invention relates to automatic tuning devices of the permeability type, such as are used to adjust the constants of radio, television and like electrical circuits. The primary aim of the invention is to provide an efiicient tuning device which will afford adjustment over a greater range in frequency in a smaller space, and in which the adjusting operation will be exceedingly simple. The invention has particular reference to an adjustable unit of the above character wherein a ferrous core is used which is in the form of a complete ring or torus, either or both of the core and its cooperating coil preferably having certain special features of construction as hereinafter disclosed in greater detail. The disclosure however should be considered as merely illustrative of the invention in its broader aspects.

In the drawings- Fig. 1 is a side view of an automatic tuner constructed to operate in accordance with the invention, the main functional parts being shown independently of their mounting.

Fig. 2 is a section on line 2-2 of Fig. 1, looking in the direction of the arrows, and also shows a type of supporting structure appropriate for accommodating a gang of units of the character shown in Fig. 1.

Fig. 3 is a section on line 3-3 of Fig. 1, looking in the direction of the arrows.

Fig. 4 is a plan view of a type of metal stamping which may be used in constructing a coil of the character shown in Figs. 1 and 2.

Fig. 5 is a plan view showing detached, the

type of core used in the device shown in Figs. 1 to 3.

Fig. 6 is a view similar to Fig. 1 but showing modified forms of coil and core structure.

The invention is shown in Figs. 1 and 2 as applied to a tuning unit having a core I in the form of a ring or torus, and which may be understood as constructed of powdered iron in known manner such that its permeability is substantially uniform throughout. However one arcuate portion of the core, which will usually be slightly less than 180 in extent, has a coating 2 of a metal such as silver, copper or aluminum which is of substantially higher electrical conductivity than the body of the core. The core member I is rotatable with respect to the coil structure which'encloses a portionthereof, and therefore, dependingupon the extent to which the coated'area 2 of- -thecore -member projects into the'coil structure," this co'ate'd area acts as a-shorted turn-which'neutralizes' or decouples the permeability of the core, and further decreases the inductance of the coil below its nominal air core value, the inductance being at a minimum when the coated section of the core coincides with the coil and at a maximum when the coated section is remote from the coil. As shown in Figs. 1 and 2, the core member I may be mounted by means of a radial arm 4 upon a rotarg spindle 5 supported by appropriate bearmgs The coil structure associated with the core may be made in juxtaposed arcuately shaped sections each partially enclosing the core, so that these sections may be joined together to constitute a helical coil or winding surrounding part of the core, without requiring that the winding be wound around the body of the core or about a coil form.

Fig. 4 shows a form of metal stamping appropriate for constructing a coil of the above character, a metal plate being stamped out to provide a series of partial helical turns 1 separated by slots-8 and each provided with inner and outer flanges 9 and I0 respectively, the adjacent half helical turns 1 being initially held in proper position to each other by bridging strips II on the inner rim of the stamping, and similar bridging strips l2 on the outer rim of the stamping. A terminal strip l3 extending from the partial helical turn at the left of Fig. 4, may also be stamped out at the same time, this strip being shown as provided with rivet holes l4 and I5 for attachment to an appropriate insulating support as hereinafter .described.

The terminal strip 13 is also shown as provided with a temporary connecting strip l6 (Fig. 4.)

shown as provided with supporting lugs l8 for attachment to an appropriate insulating support by eyelets or the like.

In assembling a coil structure of the above character, two complementary, mating metal stampings of the character shown in Fig.4 will be employed, one being right hand and the other left hand, so to speak, so that when juxtaposed as shown in Fig. 1, the partial helical turns 1 of the two sections will match up to form com-' plete helical turns surrounding the core, ad-

jacent flanges 9 and In of such turns being then suitably bonded together as by soldering and each complete turn thereby being structurally discontinuous at the bonded flanges or ends but being electrically continuous.

Then the coil structure surrounding the core may be placed in an appropriate shear, to cut off the bridge strips ll, l2 and I6, thus forming a continuous helical coil out of the assembled sections; i

In 2. I have shown a mounting structure appropriate for a gang of units of the above character, wherein the spindle 5 is journaled in end plates 19 which will be understood. as located at the opposite ends of the assembly, and each tuning unit is supported by an insulating ring 23 held in position by rods. 21- extending through the assembly. Each coil structure may be se cured to its supporting ring 20. by yelets. or

similar fastening devices passing through the terminal strips [3, and the tabs 18 if the latter be used.

Thus. the: tuning operation is exceedingly simple, requiring merely angular adjustment of spindle 5 and. the core or cores carried thereby, with respect to the corresponding coil structure or structures- Thecore being of torusform, will afford maximum permeability, and the unit will afford adjustm nt ver a large range in frequency, and will be relatively smallin displacement. As. indicated in Figs. 1 and. 4,. the pitch of the helical conducting turns making up the coil structure if desired. may be. made. different at, difierent points along. the coil. to obtain straight-line frequency tuning... i. e. avoid crowding at. the. high frequency end. of the band over which the unit. is used.

Also. it desired, the; arcuate sections H or. the coil structure above described, may be used. to provide variable capacity in the. resulting unit. As indicated Figs. 1, 3 and, 4, these arcuate sections I], being insulated. from each other and having a. dielectric. strip 22 interposed. between them and core. I, will produce a variable capacity effect in the circuit in which the. unit is used, depending upon. the angular relation of the silvered section 2 of the core with. respect to. the arcuate. sections. H which act as condenser plates or. armatures.

Also when. the unit is to be used. in the lower frequency range, the. core member. as. indicated in Fig. 6, may be constructed to afford different permeability in. difierent arcuate portions. of the body. thereof. Fig... 6- shows arcuate portions to. and [6,. one of which is relatively high and; the other relatively low in, permeability. In previous permeability tuning. units, a. limiting factor has beenthat the. so-called q. value. has beenv quite low when the core wasremote from the winding, but-with a core of the above described. character. the q value will be. relatively high in. all ositions of the. core. Incircuits of relatively low frequency, the coil. structure as. indicated. in. Fig. 6. may be in the form of a helical conductor ill, wound about an. arcuate coil form H, the core sections Ia andlb being. separately constructed of powdered iron of diiierent permeability and cemented together by an iron containing, cement, or beingv of= difierent. CXIOSSFSEGUOHEL]. areas.

While. the invention. has been disclosed. as carried: out. by tuning; devices. of the. specific con.- structions, above described, it should be understood that changes; may be made; therein without departing from the invention in its broader as.- pects, within the. SCOPCz'Of the appended claims.

l-gclaimz.

1,. A. tunes of the: character described, having a core member in ring form, and a cooperating coil member of general arcuate shape enclosing a portion of said core member and disposed substantially concentrically with respect thereto, means mounting said coil and core members to afford relative angular movement of one with respect to the other, one arcuate portion of said core: member having a coating of conductivity which is relatively high as: compared to the body of the core.

2. A tuner of the character described, having a core member in ring form and a cooperating coil member of general arcuate shape extending along: aportibnci. said core member and disposed substantially concentrically with respect thereto, means mounting said coil and core members to afford relative angular movement of one with respect to the other, said core member being of substantially uniform permeability in different arcuate portions thereof but one such arcuate portion having a coating or. higher conductivity than the body of. the core- 3-. A tuner of; the character described, having a core member in ring term, and a cooperating coil. member of general arcuate shape enclosing a. portion at said core member and disposed substantially concentrically with respect thereto, means. mounting said coil and core. members to afford. relative angular movement 0t one with respectto theother, one arcuate. portion of said coremember; having. a coating of conductivity which is relatively high as compared to the body of the core, different turns of said, coil. member being of different pitch.

4. A tuner. ot the cha acter de cribed, ha ns a ceremember or magneticmaterial in ring f rm, and a cooperating coil. member or general. arcu-t ate shape enclosing a portion of, said core. meme her and disposed substantially concentrically with respect. thereto, means. mounting. said. coil and core members. to afiord: relative angular movement of one with respect to the other, different arcuate portions of said core. member being constructed to provide different permeability characteristics thereof in different angular positions of. said. core member with. respect to said coil. member.

5. A device of the character described having a coil. member of general arcuate. shape, a. core member in ring form having a portion thereof enclosed: by said. coil? member, said. coil= member comprising. juxtaposed metal stampings. each comprising a partial. helical turn. extending part Way around. the. core, respectively adjacent. ends of said. partial turns. of. said stampingsbeing joined together to make up a series of complete helical turns encircling the adjacent portion of the core member and one'arcuate portion. or'said core.- member having a. coating of conductivity which, is relatively-high asrcompairedtothebo'dz of. the coral.

6. A tuner or the character described; having a core member in ring form; and acooperating coil member of general arcuate shape enclosing a portion of said core member and disposed substantially concentrically with respect thereto; means moun ng said. coil; and core mem ers to afford relative angular movement. oi onewi'th esp ct. to the. other. different. arcua port ons of Said core member being constructed to pr vids d fferen permeability and conductivity characteristics thereof in. different positions" f. core member with respect to coil membeasaid 0111 member also having ass c. iated therewith, arcuate juxtaposed condenser plates overlying a portion of said core member.

7. A tuner of the character described having a core member in ring form, a cooperating coil member of general arcuate shape enclosing a portion of said coil member, juxtaposed condenser armatures overlying a portion of said core member and spaced from said coil member in a circumferential direction along said core member, means mounting said core member, said coil member and said condenser armatures to afford relative angular movement between said core member and said coil member and armatures, different arcuate portions of said core member being constructed to provide different permeability and conductivity characteristics thereof in different angular positions of said core member with respect to said armatures.

8. A coil for encircling a ring shaped core, said coil comprising juxtaposed metal stampings each having the shape of an arc whose radius is substantially equal to the radius of said core and each comprising a partial helical turn, respectively adjacent ends of said partial turns of said stampings being joined together to make up a series of complete helical turns and the dimensions of each complete turn being at least equal to the corresponding cross-sectional dimensions of said core.

9. A coil comprising a plurality of juxtaposed metal stampings each comprising a partial helical turn. the partial turn of one of said stampings being mounted in complementary relationship to the partial turn of another of said one stamping respectively adjacent the end of the partial helical turn of said other stamping being bonded to said end of said partial turn of said other stamping to make up a complete helical turn and the complete helical turn thereby being structurally discontinuous at the bonded ends but being electrically continuous.

10. A coil comprising a plurality of juxtaposed metal stampings each comprising a plurality of adjacent partial helical turns, the partial turns of one of said stampings being mounted in complementary relationship to the partial turns of another of said stampings and respectively adjacent ends of said partial turns of said one stamping being bonded to respectively adjacent ends of the partial turns of the other of said stampings to make up a series of complete helical turnsand each complete turn thereby being structurally discontinuous at the bonded ends but being electrically continuous.

11. A coil comprising a plurality of juxtaposed metal stampings each comprising a plurality of helical half turns having flanges at the ends thereof, the half turns of one of said stampings being mounted in complementary relationship to the half turns of another of said stampings and respectively adjacent flanges at the ends of said half'turns of said one stamping being bonded to respectively adjacent flanges at the ends of the turns of said other stamping to make up a series of complete helical turns each having flanges thereon, each complete turn thereby being structurally discontinuous at the bonded flanges but being electrically continuous.

LYMAN G. KETCHAM.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 868,752 Barker Oct. 22, 1907 1,712,121 Scheller May 7, 1929 1,775,981 Warner Sept. 16, 1930 2,126,473 Keller Aug. 9, 1938 2,245,373 Weis et al June 10, 1941 2,354,331 Polydorofi July 25, 1944 2,568,169 Raczynski Sept. 18, 1951 FOREIGN PATENTS Number Country Date 410,217 Great Britain May 17, 1934 

